Authors:

We report studies on solid-state mechanical properties of
lamellae-forming
block copolymers composed of poly(cyclohexylethylene) (C) and
poly(ethylene)
(E). Specifically, we have investigated the effect of bridging
conformations
in the semicrystalline E block. We studied CEC, ECEC, and ECECE
architectures and found that tensile properties of C/E block
copolymers are
extremely sensitive to the fraction of ``soft'' E chains tethered
between
glassy C domains. While the CEC polymer has a strain-to-failure
of $\sim
$300{\%}, the ECEC and ECECE polymers fail at $\sim $1{\%}
strain. By
employing ECEC/CEC and ECECE/CEC blends, we have come up with a
molecular
parameter that describes a sharp brittle-to-ductile transition
and captures
the tensile properties of a broad range of C/E block copolymer
architectures
having equal sized E blocks. In another set of experiments,
increasing the
``middle-to-loose'' E block length ratio was found to toughen the
ECECE
block copolymers. We propose that these effects are related to a
critical
concentration of bridged E chains that governs the failure
mechanisms in
glassy-semicrystalline block copolymers.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.U30.4